1. Field of the Invention
The present invention relates to a magnetic resonance imaging apparatus and a magnetic resonance imaging method that perform photographing by magnetic resonance imaging using hardware of which temperature is likely to rise due to a photographing operation, such as a gradient magnetic field coil and a gradient magnetic field amplifier.
2. Description of the Related Art
When diffusion photographing where a large load is applied to a gradient magnetic field is performed in a magnetic resonance imaging apparatus, the temperature of hardware, such as a gradient magnetic field coil and a gradient magnetic field amplifier, considerably rises. There may be a case where photographing cannot be continued due to the temperature rise of the hardware.
There has been known a technique that estimates the change of the amount of residual heat of a gradient magnetic field coil on the basis of a waveform of current supplied to a gradient magnetic field coil according to a temporarily set protocol, and allows an operator to change the protocol on the basis of the estimation so that the amount of residual heat of the gradient magnetic field coil does not exceed an abortion level. (For example, see the specification of U.S. Pat. No. 6,977,501). The specification of U.S. Pat. No. 6,977,501 discloses that the photographing is stopped if the amount of residual heat of the gradient magnetic field coil exceeds the abortion level after the beginning of the photographing.
According to the above-mentioned Techniques the load of the gradient magnetic field coil may be different from an estimated value. In this case, the estimated value of the amount of residual heat of the gradient magnetic field coil is different from a real value of the amount of residual heat. If photographing is performed according to a protocol based on the estimated value when the estimated value is estimated to be small, the amount of residual heat exceeds the abortion level. For this reason, it is highly likely that the photographing is stopped. Further, when the estimated value is estimated to be large, a protocol based on the estimated value is defined to make the hardware have an excessive margin with respect to a limit, which is Inefficient. That is, if estimation accuracy is low, efficient photographing cannot be performed.